1. Field of the Invention
The present invention relates to a lens barrel or a camera body adapted for an optical apparatus having a lens arranged to be movable in an optical axis direction, such as a digital still camera, a video camera or a silver-halide camera.
2. Description of Related Art
The lens barrels of the kind mentioned above are arranged, in many cases, to drive a movable lens to move in the direction of an optical axis by enmeshing a rack with a feed screw of a stepping motor. It has been generally practiced to arrange the rack to be rotatable with respect to the movable lens and to be movable integrally with the movable lens in the optical axis direction.
The maximum drawn-in (retractable) position of the movable lens when the camera is not used for photo-taking is set by drawing the movable lens inward to a predetermined extent from a position of the movable lens detected by a position detector with the detected position used as a reference position.
In the case of the conventional arrangement mentioned above, since the rack and the movable lens are integral with each other in the optical axis direction, their relative positions never deviate from each other in this direction. Therefore, in a case where the movable lens is pushed by an external force in the optical axis direction, the rack also moves in the same direction. In such a case, the rack tends to disengage from the feed screw of the stepping motor. Such disengagement hinders the movable lens from being correctly moved in the optical axis direction, thereby making it no longer possible to do zooming or focusing in photo-taking.
In detecting the position of the movable lens with the position detector, the detection is made at an error of about xc2x10.5 mm due to the detection error of the position detector and also an error of mounting the position detector on the lens barrel. Generally, the movable lens is controlled not to collide against a fixed part of the lens barrel. However, considering an error of the detected position, the movable lens must be arranged to be brought to a stop at a position obtained by drawing out the movable lens from the fixed part of the lens barrel as much as the detected position error. The movable lens, therefore, comes to be in a state of being drawn out to an extent which corresponds to the width of the position detecting error. This arrangement, therefore, results in an increase of total length of the lens barrel obtained when the camera is not used for photo-taking.
It is a first object of the invention to provide a lens barrel which is arranged to be capable of preventing a rack from disengaging from a feed screw when a movable lens in the lens barrel is pushed by an external force in an optical axis direction.
It is a second object of the invention to provide a lens barrel arranged to reduce its total length obtained in a maximum drawn-in (retracted) state.
To attain the above objects, in accordance with an aspect of the invention, there is provided a lens barrel, comprising a shaft member extending in an optical axis direction, the shaft member having a screw part formed thereon and the shaft member being arranged to be driven by a motor to rotate on an axis thereof, a moving member having a screw-engaging part engaging the screw part of the shaft member, the moving member being arranged to move in the optical axis direction, a holding member holding a lens, the holding member and the moving member being moved together in the optical axis direction by rotation of the shaft member, an urging member arranged to urge the holding member and the moving member to move in the optical axis direction, and a stopper arranged to have the holding member to abut thereon when the holding member moves relative to the moving member against an urging force of the urging member.
In the lens barrel according to the invention, the motor is controlled to drive and cause the holding member to move up to and stop at a position immediately before where the holding member abuts on the stopper.
The lens barrel according to the invention is included in a camera body.
In the lens barrel according to the invention, the urging member is arranged to impart the urging force in such directions as to cause the holding member and the moving member to move away from each other.
Alternatively, the urging member is arranged to impart the urging force in such directions as to cause the holding member and the moving member to move toward each other.
The above and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in connection with the accompanying drawings.